Roger Grimes at InfoWorld's Security Central wrote a very good article about password management. I agree with everything he said, except Roger did not go far enough. For several of Roger's attack types password guessing, keystroke logging, and hash cracking, one of the mitigation techniques is strong (high entropy) passwords.

Weak passwords and other password issues continue to be the bane of every security manager's existence. Becky Waring from Windows Secrets reports on a Gmail vulnerability where an attacker can repeatedly guess your password using Gmail's, "Check for mail using POP3"
capability. This is a service Gmail provides that enables you to use an email client rather than the Gmail browser interface. You can read the details of the vulnerability at Full Disclosure.

The unfortunate reality is that we have reached a point in the evolution of technology that if an attacker is in a position to implement an unimpeded repetitive "guessing" attack on your password, like this Gmail vulnerability, there is no password you can remember that can survive the attack. In other words, if you can remember the password, it's too weak, and it will be cracked.

The only way you can really protect yourself is by using an automated password manager. LifeHacker has a very good review of the top choices available.One of the side benefits of these products, is that you should not have to physically type your passwords, thus reducing the risk associated with keyloggers, which I discussed in previous posts here and here.

Steve Gibson has a site called Perfect Passwords that automatically generates high entropy passwords.